I'm looking for some graded readers which can be downloaded free of charge for my students. I would particularly like to find graded readers for low levels- beginner and elementary. If you know where to find these, please get in touch.

I don't know what age group you are working with, but if they are young learners (kindergarten and up) then you could try the printable readers at hubbardscupboard.org. Click on 'literacy' on the left, and then on 'printable booklets'. There are lots of booklets there that are organized by word family, and leveled into 'stage 1' and 'stage 2'. I find them really useful!